Turbomachine chemical reactor and method for cracking

ABSTRACT

Chemical reactor (10) and method for cracking are disclosed. A process fluid is accelerated with axial impulse impellers (40A, 40B) to a velocity greater than Mach 1 and, in turn, generating a shock wave (90) in the process fluid by decelerating it in a static diffuser (70) having diverging diffuser passages (72). Temperature increase of the process fluid downstream of the shockwave cracks or splits molecules, such as hydrocarbons entrained in the process fluid, in a single pass, through a unidirectional flow path (F), within a single stage, without recirculating the process fluid for another pass through the same stage. In some embodiments, a system involving at least two turbomachine chemical reactors (110) may provide multiple successive stages of one or more axial impulse impellers (40A, 40B), paired with a diverging passage, static diffuser (70).

TECHNICAL FIELD

The invention relates to chemical reactors and methods for cracking.

BACKGROUND

Oil refineries and petrochemical plants fraction or “crack” heaviermolecular weight (MW) hydrocarbons. After cracking, the lightermolecular weight hydrocarbons are used in the petrochemical industry asfeedstock for production of other chemical compounds. In known,commercially practiced, pyrolysis-cracking processes, application ofheat and pressure in furnace-type, chemical reactors, in low oxygenenvironments, fractionalizes heavier MW hydrocarbons into variouslighter MW olefins, such as ethylene, without causing combustion. Often,the heavier MW hydrocarbon is entrained in heated steam. The steam- andhydrocarbon-containing process fluid flows through heat exchangers ofthe chemical reactor. Imparted temperature and residence time of theprocess fluid within heat exchangers are controlled to fracture theentrained hydrocarbons to the desired output, lower MW hydrocarbons.

Using the example of ethylene production by pyrolysis, a process fluidcomprising hydrocarbon and steam mixture is heated from 1220° F. to1545° F. in less than 400 milliseconds (MS), in a furnace-type chemicalreactor. The rate at which the heating is done and subsequently quenched(to halt further chemical reactions) is important for the production ofthe desired blend of hydrocarbons. Oxygen must not be present during theheating process, in order to avoid hydrocarbon combustion. The reactionprocess in the furnace-type chemical reactor requires large heat inputand relatively slow mass flow rate of the process fluid. In order tomeet output production goals, ethylene production plants employmultiple, parallel pyrolysis reactors, each requiring large thermalenergy inputs. Each additional reactor needed to meet production goalsincreases capital spending, energy consumption to heat the processfluid, plant real estate space.

It is desirable to increase mass flow of process fluid during thehydrocarbon cracking process, with lower production energy input.Increased mass flow meets production goals with less plant equipmentcapital spending and real estate space.

BRIEF DESCRIPTION OF DRAWINGS

The exemplary embodiments of the invention are further described in thefollowing detailed description in conjunction with the accompanyingdrawings, in which:

FIG. 1 is an axial cross section of a single-stage chemical reactorconstructed in accordance with an embodiment of the invention and asuperimposed, corresponding schematic of process-fluid flow through thereactor;

FIG. 2 is a perspective view of the chemical reactor of FIG. 1, withwalls of the annular housing passage shown in phantom;

FIGS. 3-4 are respective perspective and cross-sectional views of anembodiment of a non-shrouded impulse impeller, constructed in accordancewith an embodiment of the invention;

FIG. 5 is a cross sectional view of a shrouded impulse impeller,constructed in accordance with an embodiment of the invention;

FIG. 6 is an axial cross section of a single-stage, twin impulseimpeller, chemical reactor constructed in accordance with an embodimentof the invention and a superimposed, corresponding schematic ofprocess-fluid flow through the reactor;

FIG. 7 is a two-stage chemical reactor, constructed in accordance withan exemplary embodiment of the invention; and

FIGS. 8A and 8B are schematics of process-fluid flow through a pair ofturbomachine-type, chemical reactors and calculated static pressure andtemperature flow conditions of a hydrocarbon-containing process fluid,at various locations along the axial flow path F, through an exemplarychemical reactor having respective first and second stages constructedin accordance with the embodiment of FIG. 6.

To facilitate understanding, identical reference numerals have beenused, where possible, to designate identical elements that are common tothe figures. The figures are not drawn to scale.

DESCRIPTION OF EMBODIMENTS

Exemplary method and apparatus embodiments of the invention crack orfractionalize molecules in process fluids, such as hydrocarbonsentrained in steam. Chemical reactors and methods described in detailherein crack hydrocarbons in a turbomachine chemical reactor, byaccelerating the process fluid to a velocity greater than Mach 1 with anaxial impulse impeller and generating a shock wave in the process fluidby decelerating it in a static diffuser having diverging diffuserpassages. In some embodiments, static pressure of the process fluidremains relatively constant (e.g., within plus or minus ten percent) asit passes through the impulse impeller(s), but rises downstream of theshockwave. Temperature increase of the process fluid downstream of theshockwave cracks molecules, such as the entrained hydrocarbons, in asingle pass, through a unidirectional flow path, within a single stage,without recirculating the process fluid for another pass through thesame stage. In some embodiments, the temperature increase through asingle stage is greater than ten percent. Thus, in some embodiments, theprocess fluid passes through the single stage in 10 MS or less, comparedto hundreds of milliseconds in known pyrolysis-type reactors. Fastermass flow rates in the chemical reactors of the present inventionincrease production output. Unlike known pyrolysis-type reactors,external heat is not applied to the process fluid in the chemicalreactors of the present invention, in order to initiate or maintain thecracking chemical reaction. Elimination of external heating foroperating the presently described, a turbomachine chemical reactor, asotherwise required in pyrolysis-type reactors, reduces energyexpenditure.

In some embodiments, the turbomachine chemical reactor, or a sequentialchain of such reactors, has multiple successive stages of one or moreaxial impulse impellers, paired with a diverging passage, staticdiffuser. Successive stages crack additional hydrocarbons bysuccessively raising temperature of the flowing process fluid. In someembodiments, respective, multiple stages share a common housing, or arein separate, sequential housings, or they are in a combination ofseparate and common housings in a common feedstock line. In someembodiments, one or more stages in a first reactor function as apreheater of the process fluid, before its flow into a downstreamreactor. In some embodiments, quenching zones are incorporated inchemical reactors downstream of an impeller. Some quenching zoneembodiments introduce coolant fluid into the process fluid, in order tostabilize temperature of the process fluid. Other quenching zonesintroduce anti-fouling fluid into the process fluid, in order to inhibitfouling within the diffuser passages. Yet other quenching zonesintroduce both cooling and anti-fouling fluid into the process fluid.

FIGS. 1 and 2 show a chemical reactor 10, for cracking hydrocarbon in aprocess fluid. The chemical reactor 10 is a turbomachine-type chemicalreactor, including a housing 20 having a housing inlet 22, a housingexit 24. The housing inlet 22 has a radial orientation, but in otherembodiments, it has an axial configuration. The housing exit 24 has anaxial orientation, but in other embodiments, it has a radialconfiguration. Any combination of radial or axial inlets and exits forrespective inflow or outflow of process fluids are utilized in chemicalreactors disclosed herein.

The housing 20 defines an annular housing passage 26, within thecircumferential confines of a shroud wall 28. The housing passage 26defines a unidirectional, axial flow path F from the housing inlet 22 tothe housing exit 24, for receiving and cracking hydrocarbon in a processfluid that flows through the axial flow path. A process flow diagram,showing the axial flow path F, is superimposed over the structuraldrawing of the chemical reactor 10. At no point along the axial flowpath F does the process fluid reverse flow direction from the inlet 22towards the exit 24.

A rotary shaft 30, in the housing 20, is circumscribed by the annularhousing passage 26. The rotary shaft 30 is coupled to and drivenrotatively in the direction R, by a shaft-rotating power source ordriver 32, such as an electric motor, steam or gas turbine, or othercombustion engine. The rotary shaft 30 defines a shaft centerline axis34 that is in fixed orientation in the housing 20 and congruent with itsaxis of rotation.

An unshrouded, axial impulse impeller 40 is mounted about the rotaryshaft 30 within the annular housing passage 26, and in fluidcommunication with process fluid flowing between the inlet 22 and exit24 of the housing 20. The impeller 40 has an impeller hub 42 with anaxial length extending axially along the shaft centerline axis 34 of therotary shaft 30. A row of a plurality of impeller blades 50 projectoutwardly from the impeller hub 42, each of the impeller blades 50 has aleading edge 52 facing the housing inlet 22, a trailing edge 54 facingthe housing exit 24. Each impeller blade 50 has a blade tip 56 distalthe impeller hub 42 in opposed, spaced relationship with the shroud wall28 of the annular housing passage 26, and opposed concave 58 and convex60 blade sidewalls between the blade tip and the leading 52 and trailingedges 54. Each of the respective impeller blades 50 of the impulseimpeller 40 is configured, upon rotation of the rotary shaft 30, to turnthe velocity of the process fluid tangentially relative to the shaftcenterline axis 34 from a first tangential direction 62 at the bladeleading edge 52 to an opposite tangential direction 64 at the bladetrailing edge 54, and impart energy therein to discharge the processfluid from the trailing edge 54 therefrom, at a velocity greater Mach 1.For convenience, line 34A is drawn parallel to the shaft centerline axis34. In other embodiments, the axial impulse impeller is a shroudedimpeller, with a circumferential shroud coupled to distal tips of theimpeller blades.

A static annular diffuser 70, in the annular housing passage 26, isoriented between the axial impulse impeller 40 and the exit 24 of thehousing 20. The static annular diffuser 70 has a row of a plurality ofradially oriented, circumferentially spaced diffuser passages 72spanning the annular housing passage 26. Each diffuser passages 72 has afirst axial end 74 facing the axial impulse impeller 40, and a secondaxial end 76 facing the housing exit 24. In the embodiment of FIGS. 1and 2, the diffuser passages 72 are defined by opposed pairs of helicaldiffuser vanes 78. Each vane has a pair of opposing sidewalls 80 and 82,separated circumferentially by a hub wall 84. The specific vane 78structure of FIGS. 1 and 2 is a strake, having uniform wall thicknessbetween the opposing sidewalls 80 and 82. In other embodiments, thevanes have varying thicknesses, such as airfoils. Local cross section ofeach diffuser passage 72 increases from its first axial end 74 to itssecond axial end 76. Specifically, local cross-sectional height TH ofthe vane passage 72 is defined between the hub wall 84 and the shroudwall 28 of the housing annular passage 26. Local cross-sectional widthTw is defined between respective opposing sidewalls 80 and 82 betweentwo opposing vanes 78. Local cross-sectional area increase of each vanediffuser passage is accomplished by increase of local cross-sectionalheight TH and/or local cross-sectional width Tw. The diffuser passages72 are configured to decelerate process fluid therein, discharged fromthe impeller blades 50, to a speed less than Mach 1, generating a shockwave 90 in the process fluid and raising temperature thereof downstreamof the shock wave.

The chemical reactor 10 has a plurality of circumferentially spacedturning vanes 92 in the annular housing passage 26, oriented between thestatic annular diffuser 70 and the exit 24 of the housing 20. Eachturning vane 92 has a leading edge 94 facing the static annular diffuser70 and a trailing edge 96 facing the exit 24 of the housing 20. Opposedpairs of turning vanes 92 define a turning vane throat 98 there between,with locally varying height TH and width Tw. Local cross section of eachturning vane throat decreases from its respective pair of opposed,turning-vane leading edges 94 to its respective pair of opposed,turning-vane trailing edges 96, prior to discharge from the exit of thehousing 24, or to the inlet of a downstream stage of the same chemicalreactor 10 or to another, separate and discrete chemical reactor 10. Asshown in FIG. 1, the exit 24 is defined as an annular passage between anexhaust cone 100 and an exit transition 102. An optional, process-fluidquenching zone 104 is oriented axially downstream of the impeller 40,with discharge nozzles 106, for introduction of coolant fluid into theprocess fluid, in order to stabilize temperature of the process fluid.In other embodiments, the discharge nozzles 106 introduce anti-foulingfluid into the process fluid, in order to inhibit fouling within thediffuser passages 72 or any other component structures downstream of thediffuser passages. In other embodiments, one or more quenching zones areoriented at other locations downstream of the impeller 40, such as inthe annular space between the exhaust cone 100 and the exit transition102.

Axial impulse impellers and other components of the turbomachine-typechemical reactors described herein are fabricated by known manufacturingmethods, such as by joining of subcomponent hubs and blades, whetheroriginating from any one or more of forgings, castings, additivemanufacture, and/or shaped billets. The exemplary unshrouded, axialimpulse impeller 120 embodiment of FIGS. 3 and 4 has a monolithicimpeller hub 122 and impeller blades 124, formed by casting, forging,additive manufacture or shaping/cutting of a billet. The shrouded,monolithic axial-impulse impeller 126 embodiment of FIG. 5 has a hub127, blades 128, and circumferential shroud 129 at the distal tips ofthe blades.

In some embodiments at least two or more of the chemical reactors, withsequential axial impulse impellers 40 and shockwave inducing, staticannular diffusers 70 of the type shown in FIGS. 1 and 2 are sequentiallycoupled in stages. As so constructed, process fluid discharged by thestatic diffuser 70 of one reactor 10 is in fluid communication with theaxial impulse impeller 40 of another reactor. In these multi-stageembodiments, the respective reactors 10 are in separate respectivehousings 20 or in a shared common housing.

The chemical reactor 110 of FIG. 6 has a pair of axially spaced, first40A and second 40B axial impulse impellers commonly mounted about therotary shaft 30. Unless otherwise noted, structure of individualcomponents within the chemical reactor 110 is similar to those of thechemical reactor 10 of FIGS. 1 and 2. The trailing edges 54 of theblades 50 of the first impeller 40A face the leading edges 52 of theblades 50 of the second impeller 40B. A turning bucket 112 is interposedbetween the first 40A and second 40B axial impulse impellers. Theturning bucket 112 has a row of stationary turning bucket vanes 114 inthe annular housing passage 26, for aligning process fluid flowdischarged from trailing edges 54 of the first impeller blades 50 of thefirst impeller 40A parallel to leading edges 52 of the blades 50 of thesecond impeller 40B.

The two-stage, turbomachine-type chemical reactor 210 of FIG. 7,comprises a first-stage axial impeller 240A and first-stage, staticannular diffuser 270A downstream of the housing inlet 222. A sequentialsecond stage includes an axial impeller 240B and a static annulardiffuser 270B. Both of the first and second stages are oriented with ashared, common housing 220. In other embodiments, the first and secondstages are in separate housings. A process-fluid quenching zone 300 isin communication with the exhaust exit 224, axially downstream of theimpeller 240B. Nozzles 302 introduce coolant fluid into the processfluid, in order to stabilize temperature of the process fluid. In otherembodiments, the nozzles 302 introduce anti-fouling fluid into theprocess fluid, in order to inhibit fouling within chemical plantcomponents that are downstream of, and subsequently in contact with theprocess fluid.

In other embodiments, a turbomachine that incorporates a paired axialimpulse impeller and a static annular diffuser of the types used in theturbomachine-type chemical reactor 10, 110 or 210, is used to preheatprocess fluid prior to introduction into a downstream, turbomachine-typechemical reactor that generates sufficient temperature increase to crackhydrocarbons in the process fluid. The preheater includes a preheatingimpulse impeller, similar to the impeller 40 of FIG. 1, for acceleratingthe process fluid to a velocity greater than Mach 1; and a pre-heating,static annular diffuser, similar to the diffuser 70 of FIG. 1, fordecelerating the process fluid flowing therethrough to a speed less thanMach 1, generating a shock wave in the process fluid within thosediffuser passages, and raising temperature thereof downstream of theshock wave.

Joined FIGS. 8A and 8B are schematics of process-fluid flow through apair of turbomachine-type, chemical reactors 110A, 110B, and calculatedstatic pressure and temperature flow conditions of ahydrocarbon-containing process fluid, at various locations along theaxial flow path F. The exemplary chemical reactor has respective first110A and second 110B stages constructed in accordance with theembodiment of FIG. 6. As previously described, the components of thereactor 110 of FIG. 6 is substantially similar to the correspondingcomponents of the reactor 10 of FIGS. 1 and 2. Hence, designations orcomponents will be used interchangeably among all of those figures.

The reactors 110A and 110B of FIGS. 8A and 8B are shown in separaterespective housings 20A and 20B, but in other embodiments, they share acommon housing. In some embodiments, the reactor has more than twostages. One or more initial stages of other reactor embodiments arepreheaters for heating the process fluid to a temperature below thatneeded to initiate and/or sustain a cracking reaction. Then, in thoseembodiments, one or more subsequent, downstream stages crack thehydrocarbons. Specific static pressures and temperatures, as well asslopes of the static pressure and temperature curves, vary with thespecific heat and reaction rates of different process fluids/hydrocarbonmixtures. Any process fluid/hydrocarbon mixture is expected to exhibitsimilar general changes in temperature and pressure as shown in theunderlying curves of FIGS. 8A and 8B, as it flows through stages.

Referring specifically to FIG. 8A, and generally to FIGS. 1, 2, and 6,hydrocarbon-containing process fluid is introduced into the housinginlet 22/22A at a given temperature and pressure. In some embodiments,the process fluid is preheated by application of external heat in a heatexchanger, or by a shock wave induced in a turbomachine-type preheaterhaving the a paired axial impulse impeller and a static annular diffuserof the types described herein. The process fluid is accelerated bydriving the impeller 40A, whose construction is similar to the impellers40A of FIG. 6 and impeller 40 of FIG. 2. As shown in FIG. 2, rotatingblades 50 of the impeller 40 turn the velocity of the process fluidtangentially, relative to the shaft centerline axis 34 or its parallelaxis 34A, from a first tangential direction 62 the at leading-edge,axial end 52 of the impeller to an opposite tangential direction 64 at atrailing-edge 54, axial end of the impeller. The impeller 40A of FIG. 8A(as well as FIG. 6), accelerates the process fluid, without asignificant increase of either static pressure or static temperature(i.e., changes in either of plus or minus ten percent). Process fluiddischarged from the trailing edge 54 of the blades 50 of impeller 40A isdirected through the turning vanes 114 of the turning bucket 112, whichaligns its flow direction with the leading edge 52 of the blades 50 ofimpeller 40B. The impeller 40B in turn accelerates the process fluid toa higher velocity than that of the impeller 40A—above Mach 1. Processfluid is discharged from the trailing edge 54 of the blades 50 of theimpeller 40B, without a significant increase of either static pressureof static temperature (i.e., changes in either of plus or minus tenpercent). As shown in FIG. 8A, the process fluid pressure, andtemperature curves are relatively flat from the inlet 22A throughdischarge from the second impeller 40B.

Process fluid discharged from the second impeller 40B enters the staticannular diffuser 70A at the first axial end 74A. The locally increasing,cross-sectional area of the diffuser passages 72 (see e.g., FIGS. 1 and2) decelerates the process fluid to a speed less than Mach 1, causing asignificant reduction in both static temperature and pressure. Thedeceleration induces a shock wave 90A in the diffuser passages 72,somewhere along the axial length of the static diffuser 70A. Axiallocation of the shock wave 90A varies with properties of the processfluid/entrained hydrocarbons, back pressure in the axial flow path Fwithin and/or downstream of the static diffuser 70A, diffuser passage 72and/or turning vane 92 and/or housing exit 24A geometry (e.g., thelocally varying cross-section of any of them), and other factors. Theshock wave 90A induces a downstream temperature increase that issufficient to crack hydrocarbons in the process fluid. In someembodiments, the shock wave 90A raises absolute temperature of theprocess fluid from the inlet 22A of the housing to downstream of theshockwave by at least ten percent (10%), within ten milliseconds (10MS), without changing static pressure by more than plus or minus tenpercent (10%). In some embodiments, cracking reaction continues at leastpartly through the turning vanes 92A and the exit 24A, causing atemperature decrease in the process fluid, as shown by the arrowed linesegments terminating at reference number 8B. Process fluid exits thehousing exit 24A, for further processing by the second stage reactor110B.

Referring to FIG. 8B, and generally also to FIGS. 1, 2, and 6, processfluid exiting the housing exit 24A of the reactor 110A (labeled 8A) isintroduced into the housing inlet 22B. Due to heat absorption by theprocess fluid downstream of the shock wave 90A, for sustainment ofcracking reactions, temperature of the process fluid entering thehousing inlet 22B is generally lower than it was immediately downstreamof the shock wave 90A. The process fluid is re-accelerated, to a speedgreater than Mach 1, in the reactor 110B by sequential passage throughthe impulse impeller 40A, the turning bucket 112, and the impulseimpeller 40B, while respective static pressure and temperature remainrelatively stable (i.e., plus or minus ten percent).

Again, as in the reactor 110A, process fluid discharged from the secondimpeller 40B of the reactor 110B enters the static annular diffuser 70Bat the first axial end 74B. The locally increasing, cross-sectional areaof the diffuser passages 72 (see e.g., FIGS. 1 and 2) decelerates theprocess fluid to a speed less than Mach 1, causing a significantreduction in both static temperature and pressure. The decelerationinduces a shock wave 90B in the diffuser passages 72, somewhere alongthe axial length of the static diffuser 70B. Axial location of the shockwave 90B within the static annular diffuser 70B varies with propertiesof the process fluid/entrained hydrocarbons, back pressure in the axialflow path F within and/or downstream of the static diffuser 70B,diffuser passage 72 and/or turning vane 92B and/or housing exit 24Bgeometry (e.g., the locally varying cross-section of any of them), andother factors. The shock wave 90B induces a downstream temperatureincrease that is sufficient to crack hydrocarbons in the process fluid.In some embodiments, the shock wave 90B raises absolute temperature ofthe process fluid from the inlet 22B of the housing to downstream of theshockwave by at least ten percent (10%), within ten milliseconds (10MS), without changing static pressure by more than plus or minus tenpercent (10%). In some embodiments, cracking reaction continues at leastpartly through the turning vanes 92B and the exit 24B, causingtemperature and pressure decreases in the process fluid, as shown by thearrowed line segments terminating at reference number F_(OUT). In someembodiments, the turning vanes constrict flow cross sectional area ofthe process fluid. The process fluid F_(OUT) exits the housing exit 24B,for further processing. In some embodiments, a quenching zone 104 isincorporated in the second stage reactor 110B downstream of the secondimpulse impeller 40B, to control the cracking reaction rate by injectionof cooling steam or other cooling and/or anti-fouling fluids. In someembodiments, the quenching zone 104 terminates further crackingreactions. In some embodiments a quench exchanger, such as the quenchexchanger 300 of FIG. 7 is in fluid communication with the housing exit24B.

Embodiments of turbomachine-type chemical reactors disclosed hereinfacilitate cracking of hydrocarbons entrained within a process fluid,without application of external heat, as required for pyrolysis-typechemical reactors. The presently disclosed reactors, with theirunidirectional, axial flow path through an annular housing passage,assure high mass flow rate and quicker cracking reaction times thanknown pyrolysis-type chemical reactors. Fewer of the presently disclosedchemical reactors are required to process a desired, cracked hydrocarbonoutput rate than known pyrolysis-type chemical reactors; this reducesplant construction and maintenance costs.

Although various embodiments that incorporate the invention have beenshown and described in detail herein, others can readily devise manyother varied embodiments that still incorporate the claimed invention.The invention is not limited in its application to the exemplaryembodiment details of construction and the arrangement of components setforth in the description or illustrated in the drawings. The inventionis capable of other embodiments and of being practiced or of beingcarried out in various ways. In addition, it is to be understood thatthe phraseology and terminology used herein is for the purpose ofdescription and should not be regarded as limiting. The use of“including,” “comprising,” or “having” and variations thereof herein ismeant to encompass the items listed thereafter and equivalents thereofas well as additional items. Unless specified or limited otherwise, theterms “mounted”, “connected”, “supported”, and “coupled” and variationsthereof are to be interpreted broadly; they encompass direct andindirect mountings, connections, supports, and couplings. Further,“connected” and “coupled” are not restricted to physical, mechanical, orelectrical connections or couplings.

What is claimed is:
 1. A chemical reactor comprising: a housing having:a housing inlet; a housing exit; and an annular housing passage, whichdefines a unidirectional, axial flow path from the housing inlet to thehousing exit, for receiving a process fluid therein; a rotary shaft, inthe housing, circumscribed by the annular housing passage, for couplingto a shaft-rotating power source, the rotary shaft defining a shaftcenterline axis that is in fixed orientation in the housing andcongruent with its axis of rotation; a first axial impulse impeller anda second axial impulse impeller commonly mounted about the rotary shaftwithin the annular housing passage and in fluid communication withprocess fluid flowing between the inlet and exit of the housing, thefirst and second axial impulse impellers axially spaced from oneanother, with trailing edges of the first axial impulse impeller facingleading edges of the second axial impulse impeller; a row of stationaryturning bucket vanes interposed between the first and second axialimpulse impellers for aligning process fluid flow discharged fromtrailing edges of the first impeller parallel to leading edges of thesecond impeller; each impeller having: an impeller hub with an axiallength extending axially along the shaft centerline axis of the rotaryshaft; a row of a plurality of impeller blades projecting outwardly fromthe impeller hub, each of the impeller blades respectively having: aleading edge facing the housing inlet, a trailing edge facing thehousing exit, a blade tip distal the impeller hub in opposed, spacedrelationship with the annular housing passage, and opposed concave andconvex blade sidewalls between the blade tip and the leading andtrailing edges thereof; the impeller blades configured, upon rotation ofthe rotary shaft, to turn the flow of the process fluid tangentiallyrelative to the shaft centerline axis from a first tangential directionat the blade leading edge to an opposite tangential direction at theblade trailing edge, and impart energy therein to discharge the processfluid from their respective trailing edges therefrom, at a velocitygreater than Mach 1; a static annular diffuser in the annular housingpassage, oriented between the second axial impulse impeller and the exitof the housing, the static annular diffuser having a row of a pluralityof radially oriented, circumferentially spaced diffuser passagesspanning the annular housing passage; each of the diffuser passageshaving: a first axial end facing the second axial impulse impeller, anda second axial end facing the housing exit, local cross section of eachdiffuser passage increasing from its first axial end to its second axialend; the diffuser passages configured to decelerate process fluidflowing through the diffuser passages, discharged from the impellerblades, to a speed less than Mach 1, and generating within the diffuserpassages a shock wave in the process fluid and sufficiently raisingtemperature of the process fluid downstream of the shock wave to crackmolecules in the process fluid, prior to discharge of the process fluidfrom the exit of the housing; and circumferentially spaced turning vanesin the annular housing passage, oriented between the static annulardiffuser and the exit of the housing, the respective turning vaneshaving a leading edge facing the static annular diffuser and a trailingedge facing the exit of the housing, opposed pairs of turning vanesdefining a turning vane throat there between, local cross section ofeach turning vane throat decreasing from its respective pair of opposed,turning-vane leading edges to its respective pair of opposed,turning-vane trailing edges.
 2. The chemical reactor of claim 1, whereinthe respective circumferentially spaced, diffuser passages are definedbetween a shroud wall of the annular housing passage and helicaldiffuser vanes, the diffuser vanes having opposed, radially outwardlydirected vane side walls separated by a hub wall; local cross section ofthe respective diffuser passages defined by vane throat width betweenopposing, adjoining vanes and vane throat height from the hub wall tothe shroud wall of the annular housing passage, with either or bothrespective diffuser passage throat width and/or height increasing fromthe first axial end to the second axial end of the diffuser passage. 3.The chemical reactor of claim 1, further comprising a process-fluidquenching zone axially downstream of the second axial impulse impeller,for introduction of coolant fluid into the process fluid, in order tostabilize temperature of the process fluid; or for introduction ofanti-fouling fluid into the process fluid, in order to inhibit foulingwithin the diffuser passages.
 4. A system comprising: at least two ofthe chemical reactors of claim 1, sequentially coupled, with processfluid discharged by the turning vanes of one reactor in fluidcommunication with the first axial impulse impeller of another reactor,where the respective reactors are in separate respective housings or ina shared common housing.
 5. The chemical reactor of claim 1, whereineach axial impulse impeller comprises a monolithic impeller hub andimpeller blades.
 6. The chemical reactor of claim 1, further comprisinga process fluid preheater coupled to the housing inlet, for preheatingprocess fluid prior to introduction into the reactor; the process fluidpreheater including: a preheating impulse impeller for accelerating theprocess fluid to a velocity greater than Mach 1; and a pre-heatingstatic annular diffuser, for decelerating the process fluid flowingtherethrough to a speed less than Mach 1, generating a shock wave in theprocess fluid within the diffuser passages of the pre-heating staticannular diffuser, and raising the temperature thereof downstream of theshock wave.
 7. A method for cracking comprising: providing a chemicalreactor having: a housing having: a shaft centerline axis that is infixed orientation in the housing; a housing inlet; a housing exit; andan annular housing passage defining a unidirectional, axial flow pathfor the process fluid from the housing inlet to the housing exit; afirst axial impulse impeller and a second axial impulse impellercommonly mounted about the rotary shaft within the annular housingpassage to be rotatively driven about an impeller axis of rotation thatis congruent with the shaft centerline axis, the first and second axialimpulse impellers axially spaced from one another, with trailing edgesof the first axial impulse impeller facing leading edges of the secondaxial impulse impeller; a static annular diffuser within the annularhousing passage, having a first axial end facing the second axialimpulse impeller and a second axial end facing the exit of the housing,the static annular diffuser defining diffuser passages having locallyincreasing, cross-sectional area from the first to the second axial endthereof; and circumferentially spaced turning vanes in the annularhousing passage, oriented between the static annular diffuser and theexit of the housing, the respective turning vanes having a leading edgefacing the static annular diffuser and a trailing edge facing the exitof the housing, opposed pairs of turning vanes defining a turning vanethroat there between, local cross section of each turning vane throatdecreasing from its respective pair of opposed, turning-vane leadingedges to its respective pair of opposed, turning-vane trailing edges;introducing a flow of process fluid into the housing inlet; driving thefirst and second axial impulse impellers rotatively with ashaft-rotating power source, turning flow of the process fluidtangentially relative to the shaft centerline axis from a firsttangential direction at respective leading edges of blades of eachimpeller to an opposite tangential direction at respective trailingedges of blades of each impeller, and imparting energy therein,accelerating the process fluid to a velocity greater than Mach 1;aligning process fluid flow discharged from the respective trailingedges of blades of the first impeller parallel to the respective leadingedges of blades of the second impeller by interposing a row ofstationary turning bucket vanes in the annular housing passage betweenthe first and second axial impulse impellers; and discharging theprocess fluid from the second axial impeller through the diffuserpassages of the static annular diffuser, decelerating the process fluidflowing through the diffuser passages to a speed less than Mach 1, andgenerating within the diffuser passages a shock wave in the processfluid, the shock wave sufficiently raising the temperature of theprocess fluid downstream of the shock wave to crack molecules in theprocess fluid.
 8. The method of claim 7, further comprising quenchingthe process fluid with a coolant fluid, axially downstream of the secondaxial impulse impeller, in order to stabilize temperature of the processfluid; or with an anti-fouling fluid, in order to inhibit fouling withinthe diffuser passages.
 9. The method of claim 7, further comprisingconstricting flow cross sectional area of the process fluid axiallydownstream of the static annular diffuser with the turning vanes. 10.The method of claim 7, further comprising sequentially coupling at leasttwo of the chemical reactors, routing process fluid discharged by theturning vanes of one reactor to the first axial impulse impeller ofanother reactor, where the respective reactors are in separaterespective housings or in a shared common housing.
 11. The method ofclaim 7, further comprising pre-heating the process fluid prior to itsintroduction into the housing inlet of the chemical reactor, by:accelerating the process fluid with a preheating impulse impeller to avelocity greater than Mach 1; and discharging the process fluid from thepreheating, impulse impeller through diffuser passages of a pre-heating,static annular diffuser, decelerating the process fluid flowingtherethrough to a speed less than Mach 1, generating a shock wave in theprocess fluid within those diffuser passages, raising the temperaturethereof downstream of the shock wave.
 12. The method of claim 7, furthercomprising changing a position of the shock wave generated in theprocess fluid within the diffuser passages, by modifying one or more ofa cross section of the housing exit, and/or constriction of processfluid flow downstream of the static annular diffuser, and/orbackpressure of the process fluid within the static annular diffuser.13. The method of claim 7, wherein the generating of the shockwave iseffective to raise the absolute temperature of the process fluid fromthe inlet of the housing to downstream of the shockwave by at least tenpercent (10%), within ten milliseconds (10 MS), without changing staticpressure by more than plus or minus ten percent (10%).
 14. The chemicalreactor of claim 1, wherein the molecules being cracked arehydrocarbons.
 15. The method of claim 7, wherein the molecules beingcracked are hydrocarbons.